Sun Scold / Cracks   - To fire a gun it must be loaded, cocked, and trigger pulled.  So it is with tree cracks, sun scald and other problems.  Often if one who understands tree anatomy takes a closer look, you will find so called sun scold and frost cracks are actually brought on by improper planting, old wounds where the cracks begin and so forth and soon.  More on the topic: Heat from the sun may be a primary or secondary agent involved in several types of tree problems.  It is very important to know when heat is the primary agent and when it is the secondary agent.  Sun heat is primary when trees are suddenly exposed to direct sunlight.  When trees in a group are released, or when any other activity exposes the tree, the outer bark of the tree may be altered by the sudden heat.  The bark cambium is affected and the outer bark plates are flattened.  Seldom does the sun injure the vascular cambium.  The sun may also cause, as a primary agent, winter drying of trees and other woody plants.  This occurs when the soil is frozen and water absorption is stopped, yet the sunlight on the twigs and buds may cause drying of the tissues.  This type of winter sun injury is common on many woody shrubs and on some trees.  The heat of the sun may trigger the growth of buds, but the frozen soils limit the transport of water.  Periods of warm weather late in the fall or during the winter may start bud growth.  Sun or heat injury is also common where plants are growing close to white stone structures such as buildings and monuments.  The white stone acts as a mirror or magnifying glass for the heat of the sun.  The heat of the sun often causes internal cracks to develop outward.  The cracks start from wounds or dying branches and roots.  Flush cut branches often start internal problems that are made worse by sudden heat.  The heat is the trigger but not the start of the problem.  

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